Holmes MR, Gould JR, Peña-González I, Enoka RM. Force steadiness during a co-contraction task can be improved with practice, but only by young adults and not by middle-aged or old adults. Exp Physiol. 2015 Feb 01; 100(2):182-92. PMID: 25398707.

Poston B, Enoka JA, Enoka RM. Endpoint accuracy for a small and a large hand muscle in young and old adults during rapid, goal-directed isometric contractions. Exp Brain Res. 2008 May; 187(3):373-85. PMID: 18288474.